Normal sudoku rules apply. The two digits on an arrow give the coordinates of a particular target cell somewhere in the grid. The digit on the arrow's shaft indicates the target cell's row, and the digit on the arrowhead indicates the target cell's column. The difference between the two digits should be placed into the target cell. No two arrows target the same cell. Also: A pink arrow contains two consecutive digits; a green arrow contains two digits with a difference of at least 5; and, on a black arrow, one digit is double the other.